1. Field of the Invention
The present invention relates to a fiber reinforced cement mortar product made of the network of long fiber oriented and laid in the cement mortar matrix.
2. Discussion of the Background
Fibers reinforced cement mortar is widely employed, generally in form of sheet, tube, hollow plank, block, etc.
The typical example of the fiber reinforced cement mortar has been so called asbestos cement board, but recently, in view of preventing environmental pollution by asbestos, various organic and inorganic fiber have increasingly been tried as replacement.
However, most of them are made by the process of dispersing short fiber randomly to two or three dimensions in the cement mortar. So a large quantity of fiber is necessary to obtain highly strong and elastic material which usually results in making a lot of waste.
Especially, the greatest drawback, when high-tech fiber is used, is that strength and elasticity of the fiber can't be brought out and that the product is costly.
So such a process has been proposed as molding long fiber previously formed into linear strands or latticework and orienting them proponderantly in one or two dimension in the cement mortar matrix section, and improving properties of mortar.
The merit of this method is that the amount of fibers is saved to procure the same flexural or tensile strength as that of the fiber-reinforced cement where fibers are randomly oriented either in two or three dimensions. Moreover, material design is possible, and the higher the properties of the fiber, the more effectively the excellent performance of fiber can be drawn.
But former method of reinforcing by long fibers has been drawbacks that the bond between cement mortar matrix and reinforcing fiber, or between fibers aren't enough to bring sufficient strength.
On the other hand, fiber strands or rods by resin-impregnation high strength as fiber reinforced resin product is expected, but the bond between cement mortar and resin is not sufficient in itself, making the rods slip, so rods can be pulled out.
Besides, autoclaving for improving the dimensional stability of mortar causes deterioration of resin by the high temperature and alkaline environment, resulting in decline of the flexural strength of the product.
On the other hand, bond between cement mortar matrix and the fiber can be improved by roughening the surface of the fiber, or making them into fibril. However the stronger the fiber the more it fails abruptly on reaching the maximum stress, and it is disadvantageous that the reinforced material is poor in toughness.
To improve toughness of the product, more ductile fiber is employed, bond between fibers and cement mortar matrix is adjusted, and compressive failure of cement mortar matrix is induced. However, they are disadvantageous because of the difficulty of section design of the product and the lack of the quality stability.